1. Field of the Invention
This invention relates to an ozone generating apparatus by utilizing a silent discharge, particularly, relates to an ozone generating apparatus of a large capacity.
2. Description of the Related Art
Conventional ozone generating apparatuses have the configuration shown in FIG. 11. Conventional ozone generating apparatuses comprise a glass tube 1, a metal film 2 formed in an inner wall of the glass tube 1 so as to function as a high voltage electrode, a cylindrical metal tube 3 arranged outside the glass tube 1 coaxially with the glass tube so as to function as a grounding electrode. The metal tube 3 is fixed to an ozone generating tank 4 which is electrically grounded. A power feeding brush 30 is inserted inside the metal film 2, an alternating high voltage is supplied to the metal film 2 from an alternating high voltage power supply 11 provided outside the ozone generating tank 4 through a power feeding member 9. A bushing 10 is provided so as to supply the alternating high voltage in the ozone generating tank 4 which is grounded. When the alternating high voltage is applied between the metal film 2 and the metal tube 3, discharge is generated in a discharge gap 12 between the glass tube 1 and the metal tube 3. In ordinary apparatuses, a discharge gap is maintained to be 1 mm or less.
Dry air or oxygen gas to which nitrogen gas is slightly added is introduced from a gas inlet 13 which is provided at the ozone generating tank 4 and is led to the discharge gap 12. When the dry air or the oxygen gas to which the nitrogen gas is added is flowed through the discharge gap 12, oxygen in the dry air or the oxygen gas to which the nitrogen gas is added is dissociated by discharge so as to generate ozone. The generated ozone gas is exhausted from a gas outlet 14. A part of energy which is generated by discharge is used for generating ozone gas, and the rest of energy is converted to heat energy to heat the glass tube 1 and the metal tube 3. In order to cool the glass tube 1 and the metal tube 3, cooling water is flowed outside the metal tube 3 so as to prevent the glass tube from being damaged and to contribute to generating ozone efficiently. In ordinary ozone generating apparatuses, a large number of discharge tubes comprising a glass tube, a metal film and a metal tube which are fixed to an ozone generating tank 4, and alternating high voltage power is supplied in parallel from one alternating high voltage power supply 11 to the metal films formed in an inner wall of the large number of glass tubes.
When the glass tube 1 is degraded or damaged by some causes, short circuit current flows from an alternating high voltage power supply 11 to the metal film 2 formed in the inner wall of the glass tube 1. In order to cut off short-circuit current; a fuse is provided to each glass tube 1, though the fuse is not shown in FIG. 11. Alternatively, a short circuit phenomenon is detected by an alternating high voltage power supply so as to shut off the power supply. Alternatively, as described in Patent Application WO 2006-103945, a metal film 2 comprises a metal thin film, and substitution function of the fuse can be exhibited by melting and making the metal thin films disappear by short-circuit current so as to shut off the short-circuit current.
In Japanese Utility Model Application Laid-Open No. 53-160456A, a power feeding brush 30 comprises a large number of metal thin wires 31, a brush shaft 32 and a terminal 8 connected to the brush shaft. As a metal film 2 comprises a thin film, the diameter of the metal thin wire is made to be a diameter of about 0.2 mm so as not to damage the metal film 2. Further, the metal thin wire is made of stainless steel so as to prevent the deterioration caused by ozone gas. Further, in order to supply an electrical power uniformly from the power feeding brush 30 to the metal film 2, a large number of metal thin wires 31 are mounted on the brush shaft 32.
In Japanese Patent Application Laid-Open No. 8-151201, an apparatus having the configuration in which a brush comprising a brush shaft and a large number of metal thin wires is used as an electrode without using a metal film as an electrode is proposed.